1. Field of the Invention
This invention relates to a method of manufacturing a synthesis gas to be employed in the manufacture of methanol, in the manufacture of gasoline by means of GTL (Gas to Liquid) process, or in the manufacture of dimethyl ether, and also relates to a method of manufacturing methanol.
2. Description of the Related Art
A synthesis gas comprising hydrogen (H2) and carbon monoxide (CO) is employed as a raw material for synthesizing methanol for example.
This synthesis gas is conventionally manufactured by a method wherein a gaseous hydrocarbon or a vaporized liquid hydrocarbon is allowed to react, by making use of a reformer, with water vapor in the presence of a nickel catalyst at a temperature ranging from 800 to 1000xc2x0 C. to produce the synthesis gas. This synthesis gas comprises, as main components, hydrogen (H2), carbon monoxide (CO) and carbon dioxide (CO2).
In the meantime, Jpn. Pat. Appln. KOKAT Publication No. 1-180841 discloses one example of the method of manufacturing such a synthesis gas, wherein carbon dioxide existing in a combustion exhaust gas discharged from a reformer is recovered by a carbon dioxide recovery apparatus provided with a carbon dioxide absorption tower and with a carbon dioxide-absorbing liquid regenerating tower, and the carbon dioxide thus recovered is fed to the upstream side of the reformer and/or the downstream side of the reformer to obtain a synthesis gas having a desired molar ratio of H2/CO which is suitable for the synthesis of methanol.
However, as the quantity of carbon dioxide to be recovered by the carbon dioxide recovery apparatus is increased in the conventional method of manufacturing methanol, the quantity of heat required to be used in the carbon dioxide recovery apparatus is caused to increase correspondingly, thus inviting a shortage of heating sources and hence increasing the manufacturing cost of methanol.
An object of the present invention is to provide a method of manufacturing a synthesis gas having a suitable molar ratio of H2/(CO+CO2) for the synthesis of methanol, wherein the waste heat of hot synthesis gas produced in a reformer is effectively utilized as a heat source for a carbon dioxide recovery apparatus, thereby making it possible to cope with any increase in heat quantity to be used in the carbon dioxide recovery apparatus.
Another object of the present invention is to provide a method of manufacturing methanol, which is capable of producing a synthesis gas having a suitable molar ratio of H2/(CO+CO2) for the synthesis of methanol, and also capable of effectively utilizing the waste heat of hot synthesis gas produced in a reformer gas a heat source for a carbon dioxide recovery apparatus as well as a heat source for a distillation apparatus, thereby making it possible to minimize the consumption of energy.
According to the present invention, there is provided a method of manufacturing a synthesis gas comprising: reacting hydrocarbons with water vapor (steam) in a reformer to produce a synthesis gas containing hydrogen, carbon monoxide and carbon dioxide; recovering carbon dioxide from combustion exhaust gas which has been discharged from the reformer by a carbon dioxide recovery apparatus provided with a carbon dioxide absorption tower and with a carbon dioxide-absorbing liquid regenerating tower; and feeding the carbon dioxide thus recovered, as a component of raw gas, to the upstream side and/or the downstream side of the reformer;
wherein the hot synthesis gas produced in the reformer is utilized as a heat source for regenerating a carbon dioxide-absorbing liquid in the carbon dioxide-absorbing liquid regenerating tower of the carbon dioxide recovery apparatus.
According to the present invention, there is also provided a method of manufacturing methanol comprising:
reacting hydrocarbons with water vapor (steam) in a reformer to thereby produce a synthesis gas containing hydrogen, carbon monoxide and carbon dioxide;
recovering carbon dioxide from combustion exhaust gas which has been discharged from the reformer by a carbon dioxide-recovering device provided with a carbon dioxide absorption tower and with a carbon dioxide-absorbing liquid regenerating tower;
feeding the carbon dioxide thus recovered, as a component of raw gas, to the upstream side and/or the downstream side of the reformer;
producing a crude methanol by introducing the synthesis gas into a methanol-synthesizing reactor; and
distilling the crude methanol by making use of a distillation apparatus to produce a refined methanol;
wherein the hot synthesis gas produced in the reformer is utilized as a heat source for regenerating a carbon dioxide-absorbing liquid in the carbon dioxide-absorbing liquid regenerating tower, and
the hot synthesis gas produced in the reformer is utilized as a heat source for the distillation apparatus.
It is preferable, in the method of manufacturing methanol according to the present invention, that the hot synthesis is permitted to pass through a heat exchanger of the carbon dioxide-absorbing liquid regenerating tower and through a heat exchanger of the distillation apparatus, thereby enabling the hot synthesis gas to undergo the heat exchange thereof. In particular, it is preferable that the distillation apparatus is provided with a first, a second and a third distillation towers each provided with a heat exchanger, thereby enabling the hot synthesis gas from the reformer to pass successively through the heat exchanger of the second distillation tower, the heat exchanger of the carbon dioxide-absorbing liquid regenerating tower, the heat exchanger of the third distillation tower, and the heat exchanger of the first distillation tower, thus enabling the hot synthesis gas to successively undergo the heat exchange thereof.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.